Inspector: improve code assist UX

[josephjclark]

User story

The UX for code assist in Monaco in the inspector is bad, actually. This issue is a little wishlist of features/improvements that we might get to one day.

• Typescript Signatures appear at the top of the prompts, but they are not particularly helpful for our users
• We force ALL common exports into the global namespace so that they appear - but most adaptors do not export all common functions
• We show JSdoc comments, badly formatted, and with lots of annotations that don't help the user.
• We should show the first line of description to the right of the suggestion (sometimes it'll show a ts signature there - not useful)
• It can be kinda hard and fiddly to get docs for the parameters
• When a function is inserted, we should also insert the opening bracket, so that the code assist is instantly in the right place
• You can open a small suggestion prompt with ctrl-space. To get the details panel on the right, you have to ctrl + space again. This is annoying and intuitive. I'd like to work out a better way to show some help for this

Notes

Editing the appearance of the code assist is hard. We might have to switch off all default language features and develop our own custom suggestions (I'm worried about what this might mean for stuff like object properties).

The ideal solution would be to take the default suggestions and customise them - removing stuff that isn't @public for example, or updating descriptions.

This might be useful hack to this end:

const x = editor.getContribution('editor.contrib.suggestController')

This gets the suggestion controller component right outta Monaco. You can then inspect it in the debugger and trace through all sorts of interesting things, including a couple of callbacks.

So far I haven't found the exact callbacks I think we need, but I wanted to record the find.

[josephjclark]

I have had to restore the JSDoc attributes in #2669

Maybe for now we have to live with jsdoc attributes appearing in the suggestions, no matter how untidy they are.

This speaks to the idea that we need to generate our own suggestions from scratch and not use the default service.